Jeffrey Andrews-Hanna

We actually see these two opposing bulges on the moon that are explained as a result of tidal processes very early in the moon's evolution.

It's also true that the tides are ever so slightly asymmetric.

The earth side bulge is a little bit larger.

And as it's something I've explored, could we do this if the moon was really close to the earth?

In theory, yes.

In practice, I think probably no.

So very good questions.

Critically important.

So the whole idea of the magma ocean and the earliest evolution of the moon based on that comes out of the samples the Apollo astronauts brought back in terms of, you know, they brought back all of these rocks rich in a mineral called plagioclase, which is sort of a dead ringer for a magma ocean.

Another thing that

The concentration of thorium I showed on the near side, that is this big question that we're trying to understand, that was first discovered from the rocks brought back by the Apollo astronauts, where some of them were rich in creep, we call it.

So they were creep rich or creepy.

And that was something discovered by the Apollo astronauts.

Seismic data from the seismometers they put on the surface.

I think that combination of boots on the ground, landers on the ground, as well as orbiters is really, really what has been critical in understanding the moon and hopefully other planets.

So the average gravity is basically the size of the moon, like you said.

So mass and radius both come into gravity.

And then in the end, you can roughly estimate gravity based on the radius.

So it scales almost linearly with radius.

So if the moon is a fifth the size of the Earth, it should have about the fifth the gravity.